Tag: heat energy transfers

Questions Related to heat energy transfers

Thermos flask prevents loss or gain of heat by

thermo flask thermos flask heat energy transfers transfer of heat physics

  1. conduction only

  2. convections only

  3. radiation only

  4. all of the above

Show answer
Correct Option: C

Thermos flask, when closed, is an approximate

thermo flask thermos flask heat energy transfers transfer of heat physics

  1. open system.

  2. closed system.

  3. isolated system.

  4. None of these

Show answer
Correct Option: C
Explanation:

An open system is a one which can exchange matter as well as energy with the surroundings. Eg: a beaker of water. A closed system is a one which can exchange only energy with the surroundings. Eg: a liquid in a closed bottle. An isolated system is a one which cannot exchange anything with the surroundings. Eg: Thermos Flask .

Liquid nitrogen is stored at $77K$ in a vacuum flask. The surrounding atmospheric temperature in the lab is $33K$.

thermo flask thermos flask heat energy transfers transfer of heat physics

  1. After a few days, the temperature of liquid nitrogen will increase.

  2. After a few days, the temperature of the lab will decrease.

  3. After a few days, the temperature of liquid nitrogen will decrease

  4. After a few days, the temperature of liquid nitrogen will remain unchanged.

Show answer
Correct Option: D
Explanation:
Liquid nitrogen is stored at $77K$ in vacuum flask. The surrounding atmosphere temperature of the lab is $33K$.
After a few days, the temperature of liquid nitrogen will remain unchanged. Because, vacuum flask is designed to prevent heat loss by conduction, convection and radiation. So, the temperature remains unchanged.

Which of the following is an insulating component in thermos flask?

thermo flask thermos flask heat energy transfers transfer of heat physics

  1. plastic foam

  2. air

  3. vacuum

  4. All of the above

Show answer
Correct Option: D
Explanation:
Insulating component in thermos flask are plastic foam, air, vacuum.
As plastic foam is insulator, so to prevent heat to radiate plastic foam is used just after the inner layer, plastic foam is being polished to reflect the inner heat inside, as air is bad conductor of heat it does not conduct heat just outside the outer layer. Vacuum is poor conductor of heat. It is situated between two layers, which prevents heat conduction through convection.

The purpose of using vacuum flask is to store

thermo flask thermos flask heat energy transfers transfer of heat physics

  1. hot drinks.

  2. cold drinks.

  3. hot as well as cold drinks.

  4. None of these

Show answer
Correct Option: C
Explanation:
The purpose of using the vacuum flask is to store hot as well as cold drinks.
The basic concept behind using the vacuum flask is to keep the temperature of liquid constant which is being kept in the flask, no heat transfer would take place via conduction, convection or radiation.

A themoflask prevent heat loss from-

thermo flask thermos flask heat energy transfers transfer of heat physics

  1. Conduction

  2. Convection

  3. radiation

  4. all of these

Show answer
Correct Option: D
Explanation:
A thermoflask prevent heat loss from conduction, convection and radiation.
As it has insulator between two layers, it prevents the direct contact with surrounding and also stops the molecular motion for heat transfer. As it is a closed system surrounded by the layer of insulator, radiation can't even take place.

When you heat the water in a pot, it boils. What do you infer from above observation?

physics heat energy transfers heat energy heat, internal energy and work internal energy

  1. Heat is a form of energy

  2. Water can boil itself

  3. Water develops heat on its own

  4. None of the above

Show answer
Correct Option: A
Explanation:

Boiling of water requires energy. Therefore heat is a form of energy since it makes the water particles to move and do work.

When we push a huge block, our body becomes

physics heat energy transfers heat energy heat, internal energy and work internal energy

  1. Hot

  2. Cold

  3. Charged

  4. Smaller

Show answer
Correct Option: A
Explanation:

When we push a huge rock, there is no transfer of muscular energy to the stationary rock.  

Also, there is no loss of energy because muscular energy transferred into heat energy, which causes our body to become hot.

Heat, as a form of energy, flows from

physics heat energy transfers heat energy heat, internal energy and work internal energy

  1. a body of higher heat content to that of a lower heat content

  2. a body of lower heat content to that of a higher heat content

  3. a hot body to a cold body

  4. a cold body to a hot body

Show answer
Correct Option: C
Explanation:

Heat flows from a hot body to a cold body. Heat flow has nothing to do with the total heat content of the body.

Amount of heat energy present is determined by :

physics heat energy transfers heat energy heat, internal energy and work internal energy

  1. Sum total of kinetic energy and the potential energy of its molecules

  2. Sum total of mechanical energy and surface energy of its molecules

  3. Sum total of chemical energy and potential energy of its molecules

  4. All

Show answer
Correct Option: A
Explanation:

The amount of heat energy present in a body is determined by the sum total of the kinetic energy and potential energy of its molecules.